Microphone Techniques

A microphone is a transducer that converts the small pressure variations of a sound wave into a corresponding electrical signal. Sound striking a thin diaphragm makes it vibrate, and a microphone's design determines how that motion is turned into voltage. The fidelity, sensitivity and noise of the result depend on the operating principle, the size and mass of the diaphragm, and the surrounding acoustics, which is why different microphones suit different tasks.

Two principles dominate. In a dynamic microphone the diaphragm is attached to a coil of wire suspended in a magnetic field; as the diaphragm moves, the coil moves through the field and generates a voltage by electromagnetic induction, exactly as a tiny generator does. Dynamic microphones are rugged, need no power and handle high sound levels well. In a condenser microphone the diaphragm forms one plate of a capacitor; sound changes the spacing and so the capacitance, which produces a signal. Condenser microphones are more sensitive and capture fine detail but require a supply, often delivered as phantom power over the same cable that carries the signal.

Beyond the transduction method, a microphone's directional behaviour shapes what it picks up. An omnidirectional microphone responds equally from all directions, while cardioid and other directional patterns are most sensitive to sound arriving from the front and reject sound from the sides and rear. Choosing a pattern helps isolate a source and control feedback and background noise. Other transducer types, such as piezoelectric elements, are used where ruggedness or specific frequency response is needed.

Frequently asked questions

How does a dynamic microphone work?

Its diaphragm moves a coil within a magnetic field, generating a voltage by electromagnetic induction. It is rugged, needs no power and tolerates high sound levels well.

What is phantom power?

It is a DC supply, commonly delivered along the microphone cable, that powers condenser microphones and their internal electronics without needing a separate power connection.

What is a cardioid pattern?

It is a directional pickup pattern most sensitive to sound from the front and least sensitive at the rear, useful for isolating a source and reducing feedback and background noise.